1. Field
The invention is in the field of carpet or upholstery cleaning methods and apparatus which utilize ultrasonic energy to aid in the cleaning process.
2. State of the Art
Various attempts have been made to adapt the known benefits of cleaning a small item in a bath of solution which is vibrating at an ultrasonic frequency, to the cleaning of carpets and upholstery. The major problem in this regard is that the carpet or upholstery to be cleaned cannot be placed in a bath of solution. The bath of solution has to be maintained on the material to be cleaned and intimate contact between the solution and material being cleaned must be maintained. Some prior attempts have used air as a cleaning medium while others have attempted to use a cleaning solution foam. Air is a compressible fluid, however, so that the ultrasonic energy imparted to the air is quickly absorbed and disapated. Similarly, in a foam as in a solution with many air bubbles, the bubbles are compressible and quickly absorb the ultrasonic energy. Thus, most of the energy that should be used for cleaning does not reach and act on the surface to be cleaned.
The units that have used a solution as the cleaning medium have made no provision to minimize the amount of air that is in the solution or that comes into the solution from the material to be cleaned. Thus, air trapped about the fibers in the material to be cleaned may absorb the energy without much of it actually reaching the fibers. Further, the patents dealing with units using a solution all indicate that cavitation of the liquid takes place and is desirable. It has been found, however, that unless extremely high liquid pressures are used (higher than could be used in an open bottomed cleaning head), real cavitation does not take place in the liquid. The liquid inherently contains dissolved air which forms air bubbles, rather than the voids which occur during cavitation. These bubbles actually hinder the cleaning action of the solution since they absorb energy, as mentioned above.
A further problem is maintaining the solution on and above the material to be cleaned and moving such solution over the material without appreciable leakage of the solution.
3. Object
An object of the present invention is to maintain and move a quantity of ultrasonically vibrating cleaning solution over material to be cleaned while minimizing the generation of air bubbles in the cleaning solution and promoting removal of air from the material to be cleaned so that the vibrating solution penetrates about the fibers and exerts the maximum cleaning action on such fibers.